I fully understand. Think of the SF/RF series as OS's attempt to design a 2-stroke that would run more like a powerful (for its day) 4-stroke: quieter running on bigger props at lower rpms. Remember, it wasn't too long after the Hanno was in production that pattern fliers switched to 120 4-strokes. In retrospect, the SF/RF engines represent a transitional time period between the short stroke screamers turning 11x7's to the 120 4-strokes turning high pitched props.

David